The invention relates to a prechamber for an internal combustion engine, an internal combustion engine comprising a prechamber of this type and a method for configuring and/or producing a prechamber of this type.
In particular with gas engines which are operated with a lean combustion air/fuel admixture, from a specific bore size of cylinders, which is typically more than 100 mm, an ignition amplifier is used to keep a combustion rate, a center of gravity of the combustion and consequently also an achieved degree of engine efficiency at a desired level. Prechambers are typically used as an ignition amplifier, wherein in a space which is separate from a main combustion chamber but which is connected thereto by means of so-called shot channels an admixture is pre-ignited by means of an ignition device, wherein, as a result of the ignition, an excess pressure in the prechamber is produced with respect to the main combustion chamber so that very hot reaction products and non-combusted admixture flow via the shot channels from the prechamber into the main combustion chamber and ignite the admixture which is arranged at that location. In particular as a result of the large reaction surface of these flame formations discharged from the shot channels, the combustion rate in the main combustion chamber compared with the use of a simple ignition spark with a very small spark volume is generally significantly increased, whereby the combustion duration in the main combustion chamber is also shortened. In particular with particularly large cylinder bores, flushed prechambers are used in which an admixture within the prechamber compared with the admixture in the main combustion chamber can be enriched with a separate fuel supply of the prechamber.
For a stable ignition with low cyclical dispersions, a stable mixture formation which is cyclically as unchanged as possible in the prechamber is an important requirement. However, there are produced during operation of an internal combustion engine cyclical changes from one cycle to the next, for example, in the fuel supply as a result of a fuel rail dynamic, wherein in particular pressure waves run through a fuel supply device or there are formed waves which are standing at that location and which lead to fluctuating pressures in the supply region for the fuel or as a result of cyclical dispersions in the charge change, consequently in particular a gas dynamic in a charge air pipe and/or exhaust gas pipe. There are thereby produced again cyclical fluctuations in the combustion and cyclical differences which may lead to changed flow and concentration relationships in the prechamber and consequently ultimately also to cyclical dispersions in terms of the cylinder power, degree of efficiency and emissions of the internal combustion engine. In this instance, in particular the conditions for the combustion in the prechamber are determined at the time of ignition largely by the flow processes during a compression cycle prior to a top dead center which is associated with an ignition event. In particular rotationally symmetrically constructed prechambers have a very sensitive flow field compared with low cyclical differences in the charge pressure path, residual gas content, fuel flushing pressure path or other effects with the previously mentioned effects on the combustion, cylinder power and emissions since these prechambers—when viewed in a peripheral direction—do not have any outstanding regions or directions so that very easily a spontaneous symmetry breaking with a non-predictable orientation, that is to say, without any specific preferred direction, can be carried out, wherein the flow field can tilt in any direction or angular position. Therefore, the cyclical dispersions in such a prechamber are large.